(1) Field of the invention
The present invention relates to an improvement of a field-effect semiconductor device having a capacitor and a field-effect transistor (FET), at least one electrode of the FET being grounded via the capacitor. More particularly, the capacitor is formed by means of a through hole in the semiconductor substrate.
(2) Description of the Prior Art
A field-effect semiconductor device generally includes active elements, such as gallium arsenide (GaAs) FETs and diodes, and passive elements, such as capacitors, resistors, inductors, and so forth. For example, when a field-effect semiconductor device employs a self-bias circuit so that the GaAs FET can be driven by a single power supply, a capacitor should be connected between the source electrode of the GaAs FET and ground, and when the field-effect semiconductor device is a low-pass filter type of matching circuit, capacitors, inductors, and GaAs FETs should be formed in the device. As an active element, a through-hole type of GaAs FET described in detail later, is known. In a conventional through-hole type of GaAs FET, one electrode thereof is directly grounded via a through-hole electrode inserted into the through-hole. Therefore, it is impossible to connect a capacitor between the electrode of the through-hole type of GaAs FET and ground (described in detail later). Accordingly, the conventional through-hole type of GaAs FET cannot employ a self-bias circuit.
Conventionally, when a field-effect semiconductor device such as a self-bias circuit or a matching circuit is formed on a semiconductor chip, passive elements, such as capacitors or resistors, are formed at the surface of the semiconductor chip in such a manner that they have planar structures. That is, each passive element requires an area which is not used by the other elements. Therefore, these passive elements occupy a considerable area on the semiconductor chip, thereby inhibiting improvement in the integration degree and causing complex wiring to have poor grounding characteristics.
Thus, there is a need to realize a field-effect semiconductor device in which passive elements such as capacitors or resistors have lateral structures formed in the same regions as the other elements and also have structures which enable the number of manufacturing steps thereof to be decreased.